34701 datasheet(16/38 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34701

FUNCTIONAL DESCRIPTION

INTRODUCTION

FUNCTIONAL DESCRIPTION

INTRODUCTION

The 34701 power supply integrated circuit provides the

means to efficiently supply the Freescale Power QUICC and

other families of Freescale microprocessors. It incorporates a

high-performance synchronous buck regulator, supplying the

microprocessor’s core, and a low dropout (LDO) linear

regulator providing the microprocessor I/O and bus voltages.

This device incorporates many advanced features; e.g.,

precisely maintained up/down power sequencing, ensuring

the proper operation and protection of the CPU and power

system. At the same time, it provides high flexibility of

configuration, allowing the maximum optimization of the

power supply system.

FUNCTIONAL PIN DESCRIPTION

OSCILLATOR FREQUENCY PIN (FREQ)

This switcher frequency selection pin can be adjusted by

connecting external resistor RF to the FREQ pin. The default

switching frequency (FREQ pin left open or tied to VDDI) is

set to 300 kHz.

INVERTING INPUT PIN (INV)

Buck Controller Error Amplifier inverting input.

OUTPUT VOLTAGE PIN (VOUT)

Output voltage of the buck converter. Input pin of the

switching regulator power sequence control circuit.

INPUT VOLTAGE 2 PINS (VIN2)

Buck regulator power input. Drain of the high-side power

MOSFET.

SWITCH PINS (SW)

Buck regulator switching node. This pin is connected to the

inductor.

GROUND PINS (GND)

Analog ground of the IC, thermal heatsinking.

POWER GROUND PINS (PGND)

Buck regulator power ground.

BOOST DRAIN PIN (VBD)

Drain of the internal boost regulator power MOSFET.

BOOST VOLTAGE PIN (VBST)

Internal boost regulator output voltage. The internal boost

regulator provides a 20 mA output current to supply the drive

circuits for the integrated power MOSFETs and the external

N-channel power MOSFET of the linear regulator. The

voltage at the VBST pin is 7.75V nominal.

BOOTSTRAP PIN (BOOT)

Bootstrap capacitor input.

SERIAL DATA PIN (SDA)

I2C bus pin. Serial data.

SERIAL CLOCK PIN (SCL)

I2C bus pin. Serial clock.

LINEAR COMPENSATION PIN (LCMP)

Linear regulator compensation pin.

LINEAR FEEDBACK PIN (LFB)

Linear regulator feedback pin.

LINEAR REGULATOR PIN (LDO)

Input pin of the linear regulator power sequence control

circuit.

CURRENT SENSE PIN (CS)

Current sense pin of the LDO. Overcurrent protection of

the linear regulator external power MOSFET. The voltage

drop over the LDO current sense resistor RS is sensed

between the CS and LDO pins. The LDO current limit can be

adjusted by selecting the proper value of the current sensing

resistor RS.

LINEAR DRIVE PIN (LDRV)

LDO gate drive of the external pass N-channel MOSFET.

INPUT VOLTAGE 1 PIN (VIN1)

The input supply pin for the integrated circuit. The internal

circuits of the IC are supplied through this pin.

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